1. Field of the Invention
The present invention relates to a magnetic tape cassette having a cassette casing and a tape-like record medium or magnetic tape wound around reel hubs and housed in the cassette casing.
2. Description of the Prior Art
One conventional magnetic tape cassette includes a tape-like record medium or magnetic tape wound around reel hubs and housed in a cassette casing, as disclosed in Japanese Utility Model Laid-Open Gazette No. 61-79887. Each of the reel hubs comprises an outer hub member around which the magnetic tape is wound and an inner hub member that is rotatable by a hub drive shaft inserted therein. The inner hub member is axially movably fitted in the outer hub member, and held in circumferential engagement with the outer hub member so that the inner and outer hub members are rotatable in unison with each other.
The magnetic tape is wound around the outer hub members of the reel hubs and housed in the cassette casing. The inner hub members of the reel hubs, in which the respective hub drive shafts are to be inserted, have opposite open ends inserted in holes that are defined in respective upper and lower shells of the cassette casing for the reception of the hub drive shafts therein. The opposite open ends of the inner hub members have axial end faces lying substantially flush with the outer surfaces of the upper and lower shells of the cassette casing. In use, the hub drive shafts are inserted in the inner hub members. When one of the hub drive shafts is rotated about its own axis, the corresponding inner hub member is rotated to cause the outer hub member fitted thereover in circumferential engagement to rotate, thereby winding and transporting the magnetic tape from the reel hub on the other drive shaft.
When the inner hub members are axially displaced, such an axial displacement is not transmitted to the outer hub members around which the magnetic tape is wound. Therefore, the magnetic tape is prevented from being laterally displaced or skewed even when the inner hub members are axially moved with respect to the outer hub members. However, since the end faces of the inner hub members are exposed on the outer surfaces of the upper and lower shells of the cassette casing, the inner hub members may be inadvertently turned about their own axes by fingers, for example. If an inner hub member is turned about its own axis, then the circumferentially engaging outer hub member is also turned by the inner hub member, with the result that the magnetic tape wound around the outer hub members is undesirably transported, or is unduly slackened or tensioned until it may finally be stretched, torn, or otherwise damaged.
Another problem of the conventional magnetic tape cassette is that when the magnetic tape cassette is loaded into a magnetic tape recording and reproducing apparatus, the hub drive shafts directly abut against the inner hub members, and engaging teeth on the hub drive shafts tend to be caught by the inner hub members. Consequently, the hub drive shafts may not smoothly be inserted into the inner hub members, making it difficult to load the magnetic tape cassette smoothly into the magnetic tape recording and reproducing apparatus.